PHYSICS  plz help
posted by Anonymous on .
A house painter uses a chair and pulley arrangement to lift himself up the side of a house. The painter's mass is 69.2 kg and the chair's mass is 24.0 kg. With what force must he pull down on the rope in order to accelerate upward at 0.379 m/s2?
The rope that the painter pulls down on goes through a pulley and is attached the chair he is sitting on.

The force F that the painter applies to the rope is doubled by the pulley so that 2F is what accelerates the painter and chair.
Solve the equation 2F = m a, where m is the total mass (69.2 + 24.0 kg). a is the acceleration, 0.379 m/s^2
The quantity you want is F 
I got 17.7 N as my answer, but it was incorrect. I'm not sure why.

Since your trying to accelerate up you have to remember that g = 9.8. So to accelerate up you need to add 9.8 + .379, in order to find the acceleration. So it would be m = 93.2 and a = 10.179. Then solve for 2F = m*a. Answer is 474.34 N